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There are two main types of thrombosis, depending on which blood vessels are blocked.

Arterial thrombosis is when a blood clot blocks an artery. Arteries carry oxygen-rich blood from the heart around the body, so arterial thrombosis can be dangerous. If a blood clot occurs in the main arteries of the heart, this can lead to heart attack. If a blood clot occurs in the arteries to the brain, it can cause a stroke.

Venous thrombosis is when a blood clot blocks a vein. Veins carry oxygen-depleted blood from the body back to the heart, and blockages can cause serious problems. An example of venous thrombosis is deep vein thrombosis (DVT), which most commonly affects veins in the legs, such as the femoral vein. In DVT, there is the risk of a pulmonary embolism – when a clot breaks off, travels through the blood stream, and becomes lodged in the pulmonary artery, the main blood vessel to the lungs.

Blood clots can also occur in a vein near the skin. This is known as superficial thrombosis, and while it can be painful, is usually not serious.

Why do blood clots form?

Blood has the ability to clot, which is important to stop excessive bleeding in the case of an injury, such as a cut. In these instances, a blood clot forms to seal up the wound and stop the bleeding.

However, unwanted blood clots can form within the circulatory system as a result of atherosclerosis. This is the process by which plaques that are made up of fat, cholesterol, calcium and other substances build up in the walls of the arteries.

Over time, these plaques harden, narrow the opening of the arteries and restrict the blood flow. If these plaques break open, they form a blood clot that can further limit or even block the flow of blood to organs and other parts of the body.

Atherosclerosis is the main underlying cause of cardiovascular disease.

The impact

Thrombosis can lead to heart attack and stroke, amongst other cardiovascular diseases.

Cardiovascular disease is the UK's – and the world’s – number one killer, while 85 per cent of all cardiovascular deaths are due to heart attack and stroke.

The risk

There are many risk factors for thrombosis. You may have a higher risk of developing thrombosis if you:

What is HRI doing?

HRI is conducting groundbreaking research from a broad range of angles to understand thrombosis and to find innovative ways of preventing, detecting and treating the resultant cardiovascular disease.

Our Thrombosis Group is focused on determining the mechanisms underlying clot formation in healthy individuals and ultimately developing safer and more effective therapies to treat cardiovascular diseases.

Our Arterial Inflammation and Redox Biology Group is investigating unstable atherosclerotic plaque that can result in thrombosis, and how to selectively identify and treat unstable plaque.

Our Haematology Research Group aims to discover new mechanisms of blood clot formation that can lead to the development of efficient and safer antithrombotic drugs.

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